Effects of far-red light on the behaviour and reproduction of the
zoophytophagous predator Macrolophus pygmaeus and its interaction with a
whitefly herbivore
Abstract
Plants can detect neighbouring plants through a reduction in the ratio
between red and far-red light (R:FR). This provides a signal of
plant-plant competition and induces rapid plant growth while inhibiting
defence against biotic stress, two interlinked responses designated as
the shade avoidance syndrome (SAS). Consequently, the SAS can influence
plant-herbivore interactions that could cascade to higher trophic
levels. However, little is known on how the expression of the SAS can
influence tritrophic interactions. We investigated whether changes in
R:FR affect the emission of herbivore-induced plant volatiles (HIPVs),
and whether these changes influence the attraction of the
zoophytophagous predator Macrolophus pygmaeus. We also studied
how the expression of the SAS and subsequent inhibition of plant
defences affects the reproduction of M. pygmaeus in both the
presence and absence of the greenhouse whitefly ( Trialeurodes
vaporariorum) as arthropod prey. The results show that changes in R:FR
have little effect on HIPV emissions and predator attraction. However, a
reduction in R:FR leads to increased reproduction of both the predator
and the whiteflies. We conclude that shade avoidance responses can
increase the population development of M. pygmaeus directly by
reducing plant defences, and indirectly by supporting higher herbivore
densities.